Drone video of gray whales captured over a seven-year period off Oregon has revealed new details about how the giant marine mammals find and eat food.

Among the findings described in two studies published over the summer are that gray whales use different swimming techniques to collect food depending on their size and age, and that larger whales are more likely to exhale “puffs of bubbles” that help them stay underwater.

“Prior to this study, we thought any whale would exhibit either of these behaviors,” said lead author of both studies, Clara Bird, a researcher at Oregon State University’s Marine Mammal Institute. “No one really thought there was a pattern to who engaged in what behavior.”

Bird’s research also found that whales use different eating techniques depending on the depth of the water in which they search for food and the habitat of their prey. Such information could aid future conservation efforts, she added, because it provides insight into the types of habitats that may need protection to preserve whales’ access to food.

“While we are not currently actively trying to protect specific habitats, it is really important to recognize that whales of different ages may not use the same habitat due to future concerns,” Bird said. “This will help us manage them in the future.”

Parts of the gray whale population are listed as threatened under the Endangered Species Act. The entire species was once at risk of extinction due to commercial hunting. Once common in the Northern Hemisphere, gray whales are now regularly seen only in the North Pacific. According to a 2020 report from the National Oceanic and Atmospheric Administration, there were just under 27,000 people in the area in 2016.

Whales feed on amphipod crustaceans such as small shrimp and worms, which they eat by sucking water and sediment from the seabed where the creatures live and then using their baleen to filter the food. Gray whales are usually observed alone or in small groups, although large groups may be seen on feeding or breeding grounds.

Bird and her team conducted research near Newport. During seven years of sailing trips, the group tracked and recorded individual whales using drones. They identified individual whales using distinctive markers such as scars, spots or the shape of their tails.

The first study resulting from this work, published in July in the journal Animal Behavior, focused on differences in whale foraging behavior depending on their size and habitat.

The team tracked 78 gray whales during a total of 160 observations between 2016 and 2022. They observed in drone footage that younger, smaller whales often swam sideways or face-first, opening and closing their mouths to find and consume food. Meanwhile, older, larger whales tended to dive and then stay upside down in what scientists called the “headstand technique.”

The study found that the likelihood of such a headstand increased as the whale grew larger, while the likelihood of using the forward swimming tactic decreased. Water depth and type of habitat – rocky, sandy or coral reef – also played a role in the whales’ approach.

Bird attributes the change in techniques to the maturity of the whale’s muscles, as well as its level of strength and coordination.

Her team’s second study, published in August in the journal Ecology and Evolution, describes how older, larger whales release air from their vents to help them stay underwater while searching for food.

“Bubble blasts” can help a whale sink by reducing its buoyancy. Larger whales need it more because their larger lungs hold more air and have more fat, which makes them prone to floating.

The findings were based on observations of 75 whales. The burst of bubbles occurred on average 27 seconds after the whale pigeon pounced in search of food, and most of them were observed when the whales did a headstand. The older and larger the whale was, the greater the likelihood of such an outbreak.

“This kind of linking size to behavior at the individual level is the really exciting part of this study,” Bird said.

Susan Parks, a biology professor at Syracuse University who has published research on whale feeding habits but was not involved in the new study, said documenting the diversity of one whale species helps scientists avoid making false generalizations.

“When we’re trying to protect endangered species, it’s really important to understand that there can be wide variations in behavior,” Parks said. “So we can’t stop at just one observation.”

Parks also highlighted the potential of drones to collect detailed data on whales.

“There are so many unknowns about their behavior,” she said, adding that the study shows that “using drone footage to spy on what the whales were doing gave them a completely different perspective on the details of how they make a living.”